At the Guardians of the Galaxy premiere in Los Angeles on Monday, the American actress appeared to let her dress, which included a sheer floral top half, a shimmery skirt and a T-shaped belt, do the talking as she looked to have a blossoming baby bump.
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Rumours began to circulate in September that Zoe had secretly wed Marco in London, and the 36-year-old confirmed her new marital status in December during an appearance on the Jimmy Kimmel Show.
"I got married in England," Zoe revealed.
Zoe and Marco managed to keep their June nuptials a well-guarded secret from the public for several months.
"It was super small but very romantic and beautiful," a source told Us Weekly, adding that the couple had "known each other for a long time" and had "great chemistry".
The premiere for Marvel's new film Guardians of the Galaxy also featured Zoe's co-star - and former boyfriend - Bradley Cooper.
Despite walking the carpet solo, rumours have also been following Bradley that he has recently married his British girlfriend Suki Waterhouse. The pair fly constantly back and forth between London and LA, and have recently been spotted wearing matching rings.
Joining Bradley and Zoe were the film's leading man, Chris Pratt, and his wife Anna Faris, Glenn Close, Vin Diesel, and Doctor Who star Karen Gillan, who plays the villain in Guardians of the Galaxy.
The British redhead shaved her hair off for the role, her first major big studio production since leaving BBC drama Doctor Who and in the hours before the premiere tweeted: "Premiere day in LA! Excitement!!!! #GuardiansOfTheGalaxy".